1. Field of the Invention
This invention relates to synthetically derived high density liquid hydrocarbon fuel compositions.
2. Description of the Prior Art
High density liquid hydrocarbon fuels are characterized in having a net volumetric heat of combustion in excess of about 140,000 BTU/gal. A high density or energy fuel is essentially required for fueling turbojet and ramjet propelled limited volume missile systems. Beyond the need for a fuel of high energy content in order to maximize range performance of the missile, there are other critical requirements in the forefront, depending in the main, on the manner in which the missile is to be deployed. For instance in airborne deployment, the fuel must exhibit a combination of a very low freeze temperature, easy ignitability in terms of its flash point and be acceptably fluid at the low temperatures encountered. On the other hand shipborne deployment requires the use of a fuel having a relatively high flash point for safety reasons but at the same time, there is a limit whereby the low temperature properties noted for airborne deployment can be sacrificed.
A high density fuel of the foregoing type does not occur in nature but rather must be chemically synthesized. Essentially all of the current generation of such fuels commonly feature a norbornane moiety having an additional saturated cyclic hydrocarbon appendage. Such appendages include the norbornane structure itself in the case of the most exotic of these fuels; viz., RJ-5, derived from dihydrodi(norbornadiene). In some instances only a specific stereo isomer of the synthesized compound represents a suitable fuel from the standpoint of having the requisite physical properties.
The isomerized hydrogenated dimer of methyl cyclopentadiene, commonly referred to as RJ-4, currently represents the designated high density fuel for propelling shipborne missile systems. The principle drawback of this fuel resides in the fact that it is a complex mixture of isomers necessitating tedious processing in order to obtain a product having a flash point desirably not in excess of about 150 and yet having a heat content within specification. The foremost objective of the present invention is to provide a composite fuel based on a substantial to a major RJ-4 component further containing other like high density fuels designed to impart optimal physical properties to the overall composition. A correlative objective is that of employing as the RJ-4 component of the composite fuel an isomeric mixture of the indicated hydrogenated derivatives exhibiting the highest heat value associated with such mixtures.